From EAST to WEST

Over the last few weeks, two important news have been published related to the preparations towards ITER operation. These news are regarding achievements at two experimental fusion reactors that have provided key data for the ITER project and have shown that we are a step closer to produce fusion energy.

The first news is about the Experimental Advanced Superconducting Tokamak (EAST). This device is the first fully superconducting tokamak with a non-circular cross-section in the world. It was designed and constructed by China and is operating from 2006.

The Chinese Academy of Sciences has reported that EAST has achieved an electron temperature of over 100 million degrees in its core plasma during a four-month experiment carried out earlier this year in collaboration with domestic and international colleagues. Note that is about seven times more than the interior of the Sun, which is about 15 million degrees C.

This level of temperature has been achieved due to an optimized coupling of four kinds of heating techniques: lower hybrid wave heating, electron cyclotron wave heating, ion cyclotron resonance heating and neutral beam ion heating.

In addition, with ITER-like operating conditions such as radio frequency wave-dominant heating, lower torque, and a water-cooling tungsten divertor, EAST achieved a fully non-inductive steady-state scenario with extension of fusion performance at high density, high temperature and high confinement.

The plasma electron temperature over 100 million degrees achieved on EAST. (Photo: the EAST Team)

The second news is about the Tungsten (chemical symbol “W”) Environment in Steady-state Tokamak (WEST). This device was the result of a major upgrade of the Tore Supra reactor that consisted in installing tungsten walls and a divertor (2013-2016). Tore Supra was for a long time the only tokamak of this size with superconducting toroidal magnets, allowing the creation of a strong permanent toroidal magnetic field. WEST is operating from 2016 at Caradache, France, and its goal is to create long-duration plasmas.

On 31 October 2018, it was reported that WEST obtained a 37-second plasma, which is 7 seconds more than the first of five milestones (“Key Project Indicators”) that were assigned to the machine on its way to final commissioning.

When the final ITER-like actively-cooled full tungsten divertor will replace the present non-actively cooled divertor made of tungsten-covered graphite blocks and only a few actively cooled test plasma-facing units, WEST will be able to produce ITER-relevant plasmas of up to 1,000 seconds.